Beverage maker with pump noise attenuator

ABSTRACT

A beverage maker, such as a pump espresso machine, comprises a noise attenuator reducing pump noise. The noise attenuator has a housing with an inlet chamber receiving inlet flow from an inlet port, the inlet chamber having compliant walls permitting volumetric expansion. An outlet chamber in the noise attenuator housing has an outlet port and spheroidal walls. A flow-restrictor is disposed between the inlet and outlet chambers. An elastomeric insert in the housing forms the inlet chamber and at least part of the outlet chamber.

TECHNICAL FIELD

The present invention relates to beverage makers having pumps, and to noise attenuators for such beverage makers.

BACKGROUND OF THE INVENTION

Beverage makers, such as espresso machines, employ an electrically powered positive displacement pump for the delivery of water at relatively high pressure, for instance to a brewing chamber or for impelling flow through a boiler or heat exchanger. The pump casing has a bore in which a piston reciprocates, its stroke determining a working chamber, and typically with spring-loaded inlet and discharge valves. The piston may be driven at high frequency, as by magnetic induction. Due to its geometry, port timing, and speed, such pumps produce a flow ripple that excites pressure waves in the water. The uneven delivery of water flow is an inherent characteristic of such a pump that contributes primarily to the flow ripple. The pump excites water borne noise which is transmitted to valves, lines, boiler or heat exchanger and then to the structures to which those components are mounted. The structures then emit vibrations that create the greater part of the overall air borne noise emitted by the beverage maker. Therefore, there is need to reduce the water borne noise, as it is key to the reduction in the noise generated by the beverage maker. It is an object of the present invention to address this need or more generally to provide an improved beverage maker.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided a beverage maker comprising:

a pump;

a noise attenuator housing with an inlet port in communication with the pump, and an outlet port;

an inlet chamber in the noise attenuator housing, the inlet chamber receiving flow from the inlet port, the inlet chamber having compliant walls permitting volumetric expansion of the inlet chamber;

an outlet chamber in the noise attenuator housing, the outlet chamber having spheroidal walls, wherein flow from the outlet chamber passes to the outlet port, and

a flow-restrictor disposed between the inlet and outlet chambers such that flow conducted from the inlet chamber to the outlet chamber is restricted by the flow-restrictor.

The beverage maker may be an espresso machine, a tea or coffee maker, a machine for frothing milk, or the like. Although the noise attenuator housing is preferably separate from the pump or pump housing, it may be formed as a part of the pump or pump housing. The pump is preferably a positive-displacement pump.

Preferably a trapped volume of compressible material is provided in the inlet chamber which serves as a cushion volume. The water acts on the trapped volume of compressible material to absorb any pressure increases attributed to the flow ripple and subsequently expel such pressure increases as the system pressure attributed to the flow ripple decreases. Preferably the compliant walls of the inlet chamber are provided by an insert of resilient material, a cavity in the insert defining the inlet chamber, and wherein a void extends about the insert, between an outer surface of the insert and an inner surface of the housing to provide for expansion of the inlet chamber.

Preferably the flow-restrictor comprises at least one passage extending through the insert. To provide the flow restriction the cross-sectional area of the flow-restrictor is less than the cross-sectional area of the inlet port. The flow-restrictor is preferably a fixed flow restrictor as the differential pressure across the flow restrictor and system operating pressure are generally constant, however an adjustable flow-restrictor with an adjustable orifice that is selectably variable to control the size thereof could be used in the alternative to accommodate machines requiring pressure differentials and operating pressures.

Preferably at least part of the spheroidal walls of outlet chamber are formed by a concavity in the insert. Preferably at least part of the spheroidal walls of outlet chamber are formed by a recess in the housing.

Preferably the at least one passage extending through the insert comprises a plurality of passages extending through the insert.

Preferably an axis of each of the at least one passages extending through the insert is aligned with a concave face of the recess in the housing.

Preferably the insert has axially opposing ends, each end having a transverse face abutting the housing, and adjacent each annular transverse face a circumferential face abutting the housing. The transverse faces and circumferential faces are preferably annular, and serve to prevent axial movement of the insert, radial movement of the insert at the ends, and to seal the inlet and outlet chambers from the void.

Preferably the insert is formed from an elastomer, most preferably silicone.

Substantially reduced noise is produces by a beverage maker having a noise attenuator according to the invention. It is believed that there are two mechanisms that work to reduce such a ripple. The first is damping, whereby the resilient walls of the first chamber work as a damper to reduce the excitation of the ripple all frequencies. The second mechanism is pressure wave interference and cancellation. Besides being effective and efficient in operational use, by its modular and compact construction it can be readily used in a range of products The device may be economically constructed and has an overall simple design which minimizes manufacturing costs.

In another aspect the invention provides a noise attenuator for a fluid system comprising:

a housing with an inlet port in communication with the pump, and an outlet port;

an inlet chamber in the housing, the inlet chamber receiving flow from the inlet port, the inlet chamber having compliant walls permitting volumetric expansion of the inlet chamber;

an outlet chamber in the housing, the outlet chamber having spheroidal walls, wherein flow from the outlet chamber passes to the outlet port, and

a flow-restrictor disposed between the inlet and outlet chambers such that flow conducted from the inlet chamber to the outlet chamber is restricted by the flow-restrictor

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is an exploded pictorial view of a beverage maker according to the invention;

FIG. 2 is an exploded view of the noise attenuator of the beverage maker of FIG. 1, and

FIG. 3 is a sectional view through the inlet and outlet ports of the noise attenuator of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a beverage maker 10, such as a electrically-pumped espresso maker, comprises a water tank 12 from which water is drawn through a suction pipe 14 by a pump 16, such as a reciprocating piston pump driven by magnetic induction.

The pump delivers water through conduit 18 to the noise attenuator 20, from which it then passes via conduit 22 to a thermoblock 24 (comprising a combined boiler and heat exchanger). A solenoid-operated three-way valve 26 determines whether the pressurised output is directed through the boiler for discharge through the nozzle 28, or through the heat exchanger for discharge through an outlet 30 below which the porta-filter 31 may be fixed. The drawing is merely illustrative of one type of beverage maker to which the invention is applicable.

The general construction of the noise attenuator 20 is best seen in FIGS. 2. A principal component of the noise attenuator 20 is its housing 30, which as shown may be assembled from first and second shells 30 a, 30 b coupled together by screw fasteners 32 and nuts 34. The shells 30 a, 30 b may be of substantially rigid moulded polymeric construction. Flanges 36, 38 are provided with apertures for receiving the screw fasteners 32 and an O-ring 40 seals the shells 30 a, 30 b together in a fluid-tight manner. Disposed internally in the housing 30 is an elastomeric insert 42, most preferably made from a silicone elastomer.

An inlet port 44 in the noise attenuator housing 30 is in communication with the pump 16, and an outlet port 46 is connected to the conduit 22.

The insert 42 has axially opposing ends, each end having a transverse face 46 a, 46 b of annular form which abuts a complementary face of the housing 30. Adjacent, and generally perpendicular to each of the transverse faces 46 a, 46 b is a respective circumferential face 48 a, 48 b also abutting a complementary face the housing. The transverse faces 46 a, 46 b and circumferential faces 48 a, 48 b serve to prevent axial movement of the insert 42, and radial movement at the ends of the insert 42.

The insert 42 has a substantially cylindrical external surface 50, coaxial with a substantially cylindrical internal surface 52 on the housing 30, defining a void 54 between the insert 42 and the housing 30. The engagement between the housing 30 and the transverse faces 46 a, 46 b and circumferential faces 48 a, 48 b also seals the void 54 against water ingress.

A cavity in the insert 42 proximate the inlet port 44 and the walls of the housing adjacent the inlet port 44 together define an inlet chamber 56, having walls 58 of a diameter substantially larger than that of the inlet port 44. The resilience of the walls 58 and the void backing them permit volumetric expansion of the inlet chamber 56.

A flow-restrictor formed on a web 60 extending internally in the insert 42, comprises four passages 62 extending through the insert. The web 60 is planar, arranged transverse to the long axis A of the insert 42, and is relatively thinner than the walls 58. The cross-sectional area of the four passages 62 is less than the cross-sectional area of the inlet port 44 to provide the flow restriction. The flow-restrictor formed on a web 60 separates the inlet chamber 56 from an outlet chamber 64, such that flow conducted from the inlet chamber 56 to the outlet chamber 64 is restricted by passing through the passages 64.

The outlet chamber 64 has spheroidal walls, and flow from the outlet chamber 64 passes out of the noise attenuator 20 via the outlet port 46. By appropriate selection of the size of the spheroidal outlet chamber the device and be tuned to the frequency, or frequencies excited by the pump 16. In the illustrated embodiment the longitudinal axis A of the insert extends centrally through both chambers 56, 64. Axes of the inlet and outlet ports 4, 46 may be generally orthogonal to provide a compact noise attenuator, readily able to be plumbed into different beverage makers. Generally half of the spheroidal walls of outlet chamber 64 are formed by a concavity in the insert 42, and half by formed by a recess in the housing 30, the joining plane between the shells 30 a, 30 b bisecting the outlet chamber 64 at its widest section. The axes 66 of the passages 62 through the flow restrictor are aligned with a concave face 70 of the second chamber 64, specifically on the shell 30 b.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof. 

1. A beverage maker comprising: a pump; a noise attenuator housing with an inlet port, in communication with the pump, and an outlet port; an inlet chamber in the noise attenuator housing, the inlet chamber receiving flow from the inlet port, the inlet chamber having compliant walls permitting volumetric expansion of the inlet chamber; an outlet chamber in the noise attenuator housing, the outlet chamber having spheroidal walls, wherein flow from the outlet chamber passes to the outlet port; and a flow-restrictor disposed between the inlet and outlet chambers and restricting flow from the inlet chamber to the outlet chamber.
 2. The beverage maker of claim 1 wherein the compliant walls of the inlet chamber include an insert of resilient material, and a cavity in the insert defining the inlet chamber, and a void extends about the insert, between an outer surface of the insert and an inner surface of the noise attenuator housing, for expansion of the inlet chamber.
 3. The beverage maker of claim 2 wherein the flow-restrictor comprises at least one passage extending through the insert.
 4. The beverage maker of claim 2 wherein at least part of the spheroidal walls of the outlet chamber comprise a concavity in the insert.
 5. The beverage maker of claim 1 wherein at least part of the spheroidal walls of the outlet chamber comprise a recess in the housing.
 6. The beverage maker of claim 3 wherein the at least one passage extending through the insert comprises a plurality of passages extending through the insert.
 7. The beverage maker of claim 5 wherein an axis of each of the at least one passage extending through the insert is aligned with a concave face of the recess in the housing.
 8. The beverage maker of claim 2 wherein the insert has axially opposing ends, each end having a transverse face abutting the noise attenuator housing, and a circumferential face abutting the housing and adjacent each transverse face.
 9. The beverage maker of claim 8 wherein the transverse faces and circumferential faces are annular, and prevent axial movement of the insert, and radial movement of the insert at the ends, and seal the inlet and outlet chambers from the void.
 10. The beverage maker of claim 2 wherein the insert is an elastomer.
 11. The beverage maker of claim 10 wherein the elastomer is a silicone elastomer.
 12. The beverage maker of claim 1 wherein the pump is a positive-displacement pump.
 13. A beverage maker comprising: a positive-displacement pump; a noise attenuator housing with an inlet port, in communication with the pump, an outlet port, and a recess with a concave face; an elastomeric insert in the housing; an inlet chamber in the noise attenuator housing defined partially by a cavity in the insert, the inlet chamber receiving flow from the inlet port, the cavity having compliant walls permitting volumetric expansion of the inlet chamber; a void extending about the insert, between an outer surface of the insert and an inner surface of the housing for expansion of the inlet; an outlet chamber in the noise attenuator housing, the outlet chamber having spheroidal walls defined partially by a concavity in the insert, wherein flow from the outlet chamber passes to the outlet port, and at least one passage extending through the insert as a flow restrictor, restricting flow from the inlet chamber to the outlet chamber wherein an axis of the at least one passage extending through the insert is aligned with the concave face of the recess in the noise attenuator housing
 14. The beverage maker of claim 15 wherein the insert has axially opposing ends, each of the ends having a transverse face abutting the noise attenuator housing, and a circumferential face abutting the housing and adjacent each transverse face.
 15. The beverage maker of claim 8 wherein the transverse faces are annular and prevent axial movement of the insert, the circumferential faces are annular and prevent radial movement of ends of the insert, and seal the inlet and outlet chambers from the void. 